Picked up a Halo:Reach LE Slim today as an upgrade to my Pro.   
It looks and feels so much better then my old Pro, however I am a little disappointed with the noise, it is indeed quieter/less offensive in tone then my 3 year old pro but not as shockingly so as id expected.  Saying this I have not yet had a chance to really put it thought its paces yet tho which is a bit of concern, at the moment its just been running it idle at dashboard etc while i sort out my wireless headaches(more on this below) I am hoping it keeps a very similar noise level/character when its been running for a while under load for few hours, if it does that then it will be a good enough improvement over the Pro 
 
Now to the other reason for posting -
 
I Can only get both my old 360 and the new Slim to connect to router if I force the 360 to "redo" the WEP password by disconnecting and reconnecting the router/network from the wireless settings panel once system is powered up. It just will not connect to the wireless network from a fresh power up at all, however once it is up I can often get it to connect by reinputing the WEP password. Router is a Netgear DGN2000.

First: The noise is mostly vibration from the system and not from the fans (which were the big noise maker in previous models). Just install your games and it should be generally much much quieter than the older models. 
 
Second: Weird wireless problem. You could try posting on the Xbox.com forums about it. There's a fair amount of people there that may have had the same issue. An alternative though could be to just turn off your wireless security and then make your SSID hidden. That way random people won't be able to find your connection so you are a bit safer. Sure, it's pretty easy to find hidden SSIDs, but most people will never know how to do that. Just an idea.

" First: The noise is mostly vibration from the system and not from the fans (which were the big noise maker in previous models). Just install your games and it should be generally much much quieter than the older models.  Second: Weird wireless problem. You could try posting on the Xbox.com forums about it. There's a fair amount of people there that may have had the same issue. An alternative though could be to just turn off your wireless security and then make your SSID hidden. That way random people won't be able to find your connection so you are a bit safer. Sure, it's pretty easy to find hidden SSIDs, but most people will never know how to do that. Just an idea. "